Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.39	4.239%	$114.027	$114.03	$114.05	$114.00
Purchase #2	$60.56	9.688%	$66.4271	$66.43	$66.45	$66.40
Purchase #3	$181.56	8.360%	$196.7384	$196.74	$196.75	$196.70
Purchase #4	$71.69	12.285%	$80.4971	$80.50	$80.50	$80.50
Purchase #5	$84.26	6.541%	$89.7714	$89.77	$89.75	$89.80
Purchase #6	$79.33	5.380%	$83.598	$83.60	$83.60	$83.60
Purchase #7	$217.66	10.497%	$240.5078	$240.51	$240.50	$240.50
7 purchase totals =	$804.45		$871.5668	$871.58	$871.60	$871.50